The present invention relates to a filter assembly machine.
More specifically, the present invention relates to a filter assembly machine wherein filters are connected to cigarette portions by means of gummed strips of paper material, each of which is rolled about a respective tobacco article defined by two cigarette portions aligned axially with the interposition of a filter twice the length of a finished cigarette filter.
Such strips are rolled about the tobacco articles by means of a so-called rolling operation performed by feeding the articles and respective strips, by means of a conveyor drum, along a rolling channel of a width approximately equal to but no wider than the diameter of the articles. The channel is normally defined by a fixed plate facing the periphery of the conveyor drum, and which provides for frictionally rolling the articles backwards onto the respective gummed strips to form double cigarettes.
During the rolling operation, the double cigarettes being formed are rolled as described above at a speed which may only assume one value for each operating speed of the machine, and which, over and above a given value, inevitably results in tobacco fallout from the open ends of the cigarette portions.
By way of a solution to the problem, U.S. Pat. No. 4,848,371 relates to a filter assembly machine featuring a rolling station comprising a multiple-rolling wheel for transferring and rolling the articles between a supply drum and an output drum. The rolling wheel comprises a cylindrical body with a number of equally spaced peripheral cavities, each housing a revolving roller defining, with the respective cavity, a curved rolling channel of a width approximately equal to but no wider than the diameter of the article. Each roller has two diametrically opposite suction seats, into one of which an article is fed from the supply roller. As the roller rotates, the article, on abandoning the respective seat, travels at least once along the rolling channel, is wrapped inside the respective strip to form a double cigarette, and, each time it comes out of the rolling channel, is fed into the opposite seat. Each double cigarette is then transferred to the output drum.
While indeed enabling the articles to be rolled at a speed slower than that at which they are transferred between the supply and output drums, the above known filter assembly machine involves several drawbacks, due to the impossibility of using rollers of less than a given minimum diameter, without impairing the rolling operation or complicating the construction design of the rolling wheel.
On the other hand, small-diameter rollers would enable a reduction in the spacing of the rollers, and hence of the articles, on the rolling wheel, and an increase in the output of the machine for a given traveling speed.
The preference on known multiple-rolling filter assembly machines is to employ fairly large-diameter rollers, and subsequently reduce the spacing of the double cigarettes to avoid feeding them at too high a speed. Such a reduction, however, has been found to have a tendency to damage the double cigarettes, and is therefore to be avoided.